Geode LX / ThinCan / General Software BIOS - DDC failing / no EDID info

[Bart Trojanowski]

* Jordan Crouse <jordan.crouse at amd.com> [080117 16:30]:
> On 17/01/08 14:48 -0500, Bart Trojanowski wrote:
> > I got back to looking at why we get no EDID info from some units with
> > General Software BIOS.  I am trying to debug why this is happening.
> > 
> > I would love for someone that knows DDC/EDID to suggest things to try at
> > this point.
> > 
> > It was mentioned to me in passing that there is a chance that the serial
> > port could be wired on the same pins that are responsible for the
> > DDC/EDID data.  If that is the case, is there an /easy/ way to find out
> > if that has been done on this unit?
> 
> Try this:
> http://dev.laptop.org/~jcrouse/gpio-tool.c
> 
> If you run it as root, it should show the state of all of the GPIO pins.
> You're looking for IN_AUX1 to _not_ be set on GPIO3, and OUT_AUX1 and
> OUT_AUX2 to _not_ be set on GPIO4.  Section 3.2.8 in the 5536 spec has a
> table that explains this.

If I am reading it right, it looks like it's in the "bad" state:

# geode-gpio-tool 
LOW              0 1 2 3 4 5 6 7 8 9 A B C D E F
------------------------------------------------
    OUT_VAL (00) - - - X X - - - - - - - - - - - 
     OUT_EN (04) - X - X X - - - - - - - - - X X 
  OUT_DR_EN (08) - - - - - - - - - - - - - - - - 
 OUT_INV_EN (0c) - - - - - - - - - - - - - - - - 
   OUT_AUX1 (10) - X - - X - - - - - - - - - X X 
   OUT_AUX2 (14) - - - - - - - - - - - - - - - - 
  OUT_PU_EN (18) - X X X X X X - X X X X X - X X 
  OUT_PD_EN (1c) - - - - - - - - - - - - X - - - 
      IN_EN (20) X - X X X - - X - - - - - X X X 
  IN_INV_EN (24) X - - - - - - X - - - - - X - - 
  IN_FILTER (28) - - - - - - - - - - - - - - - - 
 IN_EVNC_EN (2c) - - - - - - - - - - - - - - - - 
  READ_BACK (30) - - - X - - - - - - - - - - X X 
    IN_AUX1 (34) - - X X - - - - - - - - - - X X 
   EVENT_EN (38) X - - - - - - X - - - - - X - - 
  IN_POS_EN (40) - - - - - - - - - - - - - - - - 
  IN_NEG_EN (44) - - - - - - - - - - - - - - - - 
 IN_POS_STS (48) X - - X X - - X - - - - - X - - 
 IN_NEG_STS (4c) X - - X X - - X - - - - - X - - 
HIGH             0 1 2 3 4 5 6 7 8 9 A B C D E F
------------------------------------------------
    OUT_VAL (00) - - - - - - - - - - - - - - - - 
     OUT_EN (04) - - - - - - - - X - - X - - - - 
  OUT_DR_EN (08) - - - - - - - - - - - X - - - - 
 OUT_INV_EN (0c) - - - - - - - - - - - - - - - - 
   OUT_AUX1 (10) - - - - - - - - X - - - - - - - 
   OUT_AUX2 (14) - - - - - - - - - - - - - - - - 
  OUT_PU_EN (18) X X X X X X X X X X X X X X X X 
  OUT_PD_EN (1c) - - - - - - - - - - - - - - - - 
      IN_EN (20) - - - - - - - - - X - - X - - - 
  IN_INV_EN (24) - - - - - - - - - X - - - - - - 
  IN_FILTER (28) - - - - - - - - - X - - - - - - 
 IN_EVNC_EN (2c) - - - - - - - - - - - - - - - - 
  READ_BACK (30) - - - - - - - - - - - - - - - - 
    IN_AUX1 (34) - - - - - - - - - - - - X - - - 
   EVENT_EN (38) - - - - - - - - - X - - - - - - 
  IN_POS_EN (40) - - - - - - - - - - - - - - - - 
  IN_NEG_EN (44) - - - - - - - - - X - - - - - - 
 IN_POS_STS (48) - - - - - - - - - - - - - - - - 
 IN_NEG_STS (4c) - - - - - - - - - - - - - - - - 

    MAP_X            MAP_Y
0 - (INT) bit 1  8 - (INT) bit 0
1 - (INT) bit 0  9 - (INT) bit 0
2 - (INT) bit 0  10 - (INT) bit 0
3 - (INT) bit 0  11 - (INT) bit 0
4 - (INT) bit 0  12 - (INT) bit 0
5 - (INT) bit 0  13 - (INT) bit 4
6 - (INT) bit 0  14 - (INT) bit 0
7 - (INT) bit 2  15 - (INT) bit 0


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